TO THE LOWER ANIMALS 253 



restricted to one disk-like spot. Hence, while the placenta 

 of the Dog is like a girdle, that of Man has the cake-like 

 form, indicated by the name of the organ. 



But, exactly in those respects in which the developing 

 Man differs from the Dog, he resembles the ape, which, 

 like man, has a spheroidal yelk-sac and a discoidal 

 sometimes partially lobed placenta. 



So that it is only quite in the later stages of develop- 

 ment that the young human being presents marked 

 differences from the young ape, while the latter departs 

 as much from the dog in its development, as the man 

 does. 



Startling as the last assertion may appear to be, it is 

 demonstrably true, and it alone appears to me sufficient 

 to place beyond all doubt the structural unity of man 

 with the rest of the animal world, and more particularly 

 and closely with the apes. 



Thus, identical in the physical processes by which he 

 originates identical in the early stages of his formation 

 identical in the mode of his nutrition before and after 

 birth, with the animals which lie immediately below him 

 in the scale Man, if his adult and perfect structure be 

 compared with theirs, exhibits, as might be expected, a 

 marvellous likeness of organization. He resembles them 

 as they resemble one another he differs from them as 

 they differ from one another. And, though these differ- 

 ences and resemblances cannot be weighed and measured, 

 then- value may be readily estimated ; the scale or standard 

 of judgment, touching that value, being afforded and 

 expressed by the system of classification of animals now 

 current among zoologists. 



A careful study of the resemblances and differences 

 presented by animals has, in fact, led naturalists to arrange 

 them into groups, or assemblages, all the members of 

 each group presenting a certain amount of definable 

 resemblance, and the number of points of similarity being 

 smaller as the group is larger and vice versd. Thus, all 

 creatures which agree only in presenting the few distinctive 

 marks of animality form the ' Kingdom ' ANIMALIA. The 

 numerous animals which agree only in possessing the special 

 characters of Vertebrates form one ' Sub-kingdom ' of this 

 Kingdom. Then the Sub-kingdom VERTEBRATA is sub- 

 divided into the five ' Classes/ Fishes, Amphibians, Reptiles, 



